What Maintenance is Required for Polycrystalline Solar Panels？

Regular cleaning to remove dust and debris can improve efficiency by up to 5%. Check electrical connections annually for corrosion, ensure inverters are functioning correctly, and monitor output for any unexpected drops that could indicate a fault.

Cleaning Dust and Debris

Last month, I just finished handling a 23MW agrivoltaic project in Jiangsu, where the module surfaces were covered with poplar fluff like a quilt. The O&M supervisor, Lao Zhang, was so anxious that he slapped his thigh: "Three months without cleaning, and power generation dropped directly by 12%. The loss is three times more expensive than hiring a cleaning team!"

The surface of polycrystalline silicon modules is like a phone screen protector; dust accumulation can't be solved by simply wiping it off. Especially in northern sandy areas, PM10 particles form a frosted layer. Last year, a station in Ningxia used high-pressure water guns to clean, which resulted in invisible scratches on the anti-reflection film, causing a permanent 0.8% drop in annual power generation efficiency.

Blood and Tears Experience:

· Never wipe when morning dew hasn’t dried, as calcium and magnesium ions in water stains will cause scaling

· Bird droppings must be handled within 72 hours; acidic substances will corrode the EVA adhesive film

· Dry brushing requires a rotating soft-bristle brush; ordinary brooms are tools for destruction

The Gobi Desert project I handled in Qinghai had an ingenious trick: using drones equipped with thermal imaging cameras to scan. Any module with a temperature 2°C higher than the surrounding area was directly marked as a key cleaning zone. Last year, this method kept dust losses within 4%, 7 percentage points lower than the industry average.

Checking Electrical Connections

Last winter, a power station in Inner Mongolia had a laughable incident: the string voltage showed normal, but no electricity was generated. It turned out that snowmelt had entered the MC4 connector, causing the oxide layer to push the contact resistance up to 0.8Ω, far exceeding the 0.2Ω limit specified by IEC 62548 standards.

A coastal power station in Guangdong suffered a hidden loss: the waterproof rubber ring of the connector aged after two years, causing insulation resistance to plummet to 2MΩ during the rainy season (IEC requires >50MΩ). Now we require using a megohmmeter to test insulation every quarter, especially in areas with humidity >80%.

Recently, there was a typical case: a distributed project in Hebei used a non-brand connector, where the contact point coating thickness was only 0.2μm (industry standard is 0.8μm), and it oxidized and became scrap after three years. Now we specify Stäubli's MC4-Evo2, which is 30% more expensive but has a warranty period of up to 25 years.

Panel Damage Repair

Last summer, while conducting a health check on a 50MW agrivoltaic power station, we found spider-web patterns in the EL imaging of modules in Array No. 3 — a typical feature of silicon wafer micro-cracks. The power station was already under grid connection deadline pressure, and every day of delay incurred a penalty of 46,000 kWh. TÜV-certified field engineer Lao Zhang climbed onto the rack with a thermal imager, muttering, "This is even thornier than handling the PID effect at a Qinghai power station last year."

Polycrystalline silicon modules fear three types of internal damage most:
1. Micro-cracks: Like hairline cracks in glass, showing as radial black spots in EL testing
2. Hot spots: Local temperature can soar to 120°C, roasting the EVA adhesive film until it emits a burnt smell
3. PID effect: The entire string of modules may suddenly lose 20% power, similar to aging mobile phone batteries

In a case handled last week, a 182mm large-size module suffered edge frame deformation due to transportation jolts, causing three cells to develop micro-cracks. The O&M team did the following:
① Use infrared camera to lock abnormal temperature points (red alert if temperature difference >5°C)
② Confirm crack direction with EL tester
③ Remove damaged cells with a constant temperature soldering iron, a job more delicate than repairing a mobile phone motherboard
④ Replace new cells, ensuring welding temperature is 245±5°C; one shaky hand and it's ruined

According to NREL's 2023 module failure report (NREL/TP-6A20-80926), uneven stress on the frame increases the risk of micro-cracks by 47%. After Typhoon in 2022, 37% of modules at a power station in Guangdong developed edge micro-cracks, causing power generation to drop to 82% of the design value.

PID effects are even more troublesome. Last month, in a Shandong project, we found a string of modules that performed normally during the day but weakened on cloudy days — a typical potential-induced degradation. The solution is to apply reverse voltage to the modules at night, similar to defibrillating a heart. LONGi’s Hi-MO 5 modules undergo 96-hour PID testing before leaving the factory, but the issue can still recur at site humidity levels over 85%.

New repair equipment is quite interesting; a handheld photoluminescence detector developed by an Israeli company can scan micro-cracks within 30 seconds. However, veteran technicians still trust the EL tester more, as it provides visible and tangible results. Once, I saw Lao Zhang applying conductive paste to the grounding point of the frame after repairing a module, saying it's the same principle as rust-proofing car grounding wires.

Tracking System Maintenance

Last winter, a 200MW power station in Ningxia suffered a major setback with its tracking system — single-axis trackers emitted pig-slaughtering-like screeches during rotation, which turned out to be caused by sand entering the slewing bearing. The O&M supervisor, Lao Wang, was so frustrated that he slapped his thigh: "We should've learned from Trina Solar's SmartTrack system, which comes with self-cleaning tracks."

The three critical points of tracking systems:
1. Angle error: Don’t underestimate a 0.5° deviation, as it can cause a 1.2% difference in annual power generation
2. Motor lifespan: Gearbox oil temperature exceeding 65°C should trigger a warning
3. Communication delay: Group controller response exceeding 200ms drags performance

Last quarter, while maintaining a project in Xinjiang, we found the elevation angle sensor clogged with bird droppings. This device requires precision of ±0.1°, more sensitive than a mobile phone gyroscope. Cleaning requires gently wiping with an alcohol swab, similar to cleaning a DSLR camera lens. We also applied Chevron SRI-2 grease to the gears, which maintains fluidity even at -30°C.

According to CPIA's 2024 Tracking System White Paper, failure rates of unmaintained single-axis systems are seven times higher than those with regular maintenance. Test data from a tracking bracket manufacturer shows that regularly lubricated slewing bearings wear only 0.03mm over five years.

Maintaining communication systems tests skill even more. Once, we encountered a "chaos" situation with a string-type tracking system, where eastern brackets turned westward and western ones southward — it turned out to be oxidation of CAN bus connectors. Now we’ve learned our lesson: every connector gets a coat of Dow Corning DC-4 conductive paste, opposite to applying insulating grease on car spark plugs.

Recently, we’ve been experimenting with predictive maintenance — installing vibration sensors on drive motors, similar to equipping cars with OBD diagnostic systems. Data is analyzed using LSTM models, allowing prediction of gearbox failures up to 7 days in advance. Last time, we successfully warned of a broken tooth risk in Reducer Area No. 1, avoiding the scrapping of a total assembly worth 230,000 yuan.

Winter Snow Prevention Measures

Old Zhang, with 10 years of experience in PV operation and maintenance, witnessed a disastrous scene last winter at a power station in Zhangjiakou — six rows of modules collapsed like dominoes, causing a direct loss of 2.3 million yuan. Now let me share some practical snow prevention tips.

The module tilt angle must be adjusted according to the direction of snowfall. In places like Inner Mongolia where snow hits hard, it’s best to adjust the brackets to over 45 degrees. But don’t just aim for steepness; structural load-bearing capacity must be calculated:

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A 20MW power station in Ningxia implemented an effective "sloped snow removal solution" in 2023 — using thermal imaging cameras to monitor when module surface temperatures drop to -5°C during continuous snowfall, automatically activating heating films. The power consumption of these devices must be controlled to not exceed 15% of the day's power generation; otherwise, it becomes a financial loss.

· Snow clearing in the morning should be done when module temperatures are above -3°C (to prevent glass breakage due to excessive temperature differences)

· Never use a shovel to scrape snow forcefully; a power station in Hebei had 136 micro-cracked modules last year because of this

· The concentration of snow-melting agents must be kept below 5%; otherwise, aluminum frame corrosion speeds up by 3 times

The Tongyu Power Station in Jilin tested a "vibration snow removal" technology last year. Brackets were equipped with eccentric wheel motors, which automatically activated vibration mode when snow accumulation reached 15cm. However, the vibration frequency must be controlled between 28-32Hz; otherwise, junction boxes may fall off.

Regular Performance Testing

Old Wang, with 8 years of testing experience, says that modules are like middle-aged physical exams — looking only at power generation is like measuring blood pressure alone; professional equipment is needed to examine internal components. Last week, we discovered earthworm-like black lines in EL imaging of a batch of 182mm modules, which turned out to be EVA delamination.

IV curve testing should be conducted at noon when irradiance exceeds 800W/m² for accurate data. For Huawei smart inverters, be alert when the MPPT voltage fluctuates by more than 2%. Here’s a comparison of measured data:

A 50MW power station in Qinghai suffered hidden losses — power generation looked normal, but EL testers revealed micro-cracks in 23% of the modules. Later, drone-mounted infrared detection found hotspot temperatures reaching as high as 87°C, with actual power output dropping to 76% of the rated value.

· Perform at least one insulation resistance test annually (twice in humid areas)

· Grounding resistance must not exceed 4Ω, as it can attract lightning

· Torque testing of bracket screws must use digital torque wrenches; manual feel is unreliable

A fishery-solar complementary project in Guangdong went even further — installing intelligent sensors on each string of modules to monitor 15 parameters in real-time, including operating temperature and current dispersion rate. When backsheet temperature suddenly rises by 2°C/minute, the system automatically triggers an alarm, detecting faults 6-8 hours earlier than traditional methods.